Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $87.50   9.668%   $95.9595   $95.96   $95.95   $96.00  
  Purchase #2 $159.56   8.175%   $172.604   $172.60   $172.60   $172.60  
  Purchase #3 $203.77   3.429%   $210.7573   $210.76   $210.75   $210.80  
  Purchase #4 $48.98   4.639%   $51.2522   $51.25   $51.25   $51.30  
  Purchase #5 $203.61   13.751%   $231.6084   $231.61   $231.60   $231.60  
  Purchase #6 $44.75   4.493%   $46.7606   $46.76   $46.75   $46.80  
  Purchase #7 $160.87   8.381%   $174.3525   $174.35   $174.35   $174.40  
  7 purchase totals = $909.04       $983.2945   $983.29   $983.25   $983.50